cal maturation (i.e., increase in water content and hyaluronic acid, and collagenase activation) (Ikuta et al., 1991). Data obtained during first- and second-term pregnancy termination, and in IUFD, have shown that RU 486 is also able to induce cervical maturation in humans. Several placebo-controlled studies have been performed to evaluate the efficacy of RU 486 in cervical ripening prior to vacuum aspiration. Their results are summarized in Table B6.3.

The table shows that except in two studies [Rådestad et al., 1988, where the compound was given at a relatively small dose, 100 mg bid (twice a day), with measurements 24 hours after the last dose, and study FCH/85/486/21, where RU 486 was given only 12 hours prior to the measurements], RU 486 always induced a significant increase in the cervical diameter. Information obtained from trials other than those described above includes the following:

The time lag between the last RU 486 intake and the measurement of cervical diameter is an important factor. In a Canadian study (Lefèbvre et al., 1990) where several doses of RU 486 were evaluated, the cervical modifications were always significantly more important after 48 hours than after 24 hours. A similar finding was reported by Rådestad et al. (1990).

There is a dose-response relationship between dose of RU 486 and cervical diameter 24 to 48 hours after administration. The optimal dose of RU 486 was studied in the aforementioned Canadian study, in which different groups received either a placebo or 50, 100, 200, 400, or 600 mg of RU 486, as a single administration 24 or 48 hours prior to cervical calibration. For all doses of RU 486 studied, there was a significant increase of cervical diameter, which was linearly related to dosage up to 400 mg. Interestingly, in this study the duration of the subsequent vacuum aspiration was significantly decreased in parallel with the dose